Specific Aims Increasing the proportion of people living with HIV who know their serostatus is critical to containing the HIV epidemic in sub-Saharan Africa. In Kenya, approximately 1.6 million people are living with HIV and it is estimated that 53% of HIV-infected Kenyans are unaware of their status1. Although numbers of adults tested for HIV increased more than 6-fold between 2008 and 2010 in Kenya, testing rates have been stable since 2010 and significant gaps in testing are being identified. While it is not surprising that members of key populations are often not reached with standard testing strategies, it is surprising that 25-50 year old men are significantly less likely to test and link to care if infected. This proposal will focus on this latter demographic. In 2014 only 45% of men reported that they had tested in the last year compared to more than 53% of women 2, and it is essential that new testing strategies that narrow existing gaps be adopted if Kenya is to reach the first ?90? in the UNAIDS 90-90-90 by 20203. Specifically, if Kenya is to move from about half of persons living with HIV (PLWH) knowing their status to 90%, greater progress needs to be made in HIV testing men and linking them to care. While there will be additional challenges once linked to care, the first step in the cascade is critically important, a step upon which all others are dependent for success. Last year we successfully completed a cluster randomized clinical trial (RCT) of assisted partner services (aPS) to promote testing of individuals at high risk for HIV infection, many of whom were unaware of their status and had not previously tested.4-6 The aPS intervention involves notifying sexual partners of individuals diagnosed with HIV and offering testing and linkage to care. As a public health strategy to prevent the transmission of HIV through testing and treating the sexual partners of infected index cases, aPS is widely adopted in the US and Europe but has not been scaled up in sub-Saharan Africa. Our trial took place in central and western Kenya where we employed and trained study staff to deliver aPS in 18 different facilities, and determined that aPS is safe and highly effective for HIV case finding and linkage to care under these conditions.4,5 Despite this trial showing efficacy and the World Health Organization releasing guidelines in November 2016 promoting partner services7, rolling out aPS at scale will be challenging. Effectiveness of an intervention when integrated into existing health systems is usually lower than the efficacy determined in controlled trials due to weaknesses in health systems and differences in intervention delivery. Implementation science advocates for more real life research that utilizes existing systems to deliver interventions at scale and this is what this project aims to do. We propose to study the effectiveness and feasibility of aPS in Homa Bay and Kisumu, two Kenyan counties with the highest HIV prevalence in the country, and generate evidence that will ensure rapid and sustainable implementation across the region. We will accomplish these objectives through the following Specific Aims: AIM 1. Evaluate effectiveness of assisted partner services (aPS) when integrated within an existing Kenya Ministry of Health (MOH) health initiative, APHIAplus, to strengthen HIV services in western Kenya by determining that aPS improves HIV testing rates among men, identifies new HIV infections among men, and links these men to HIV care and treatment, as measured by viral suppression 12 months after diagnosis. Leveraging the completed RCT, we are in a unique position to assess the following outcomes: 1)HIV testing among men who have never tested 2) New male HIV infections and HIV-discordant couples 3) Linkage to care by 6 weeks and initiation of ART by 6 months for HIV-infected men identified by aPS 4) Suppression of plasma HIV RNA levels at 12 months among these HIV-infected men AIM 2. Determine fidelity, feasibility, cost and cost-effectiveness of implementing integrated aPS services among HIV-infected adolescent girls and women through existing HIV services. We will generate evidence to inform effective scale-up and sustainability of aPS, focusing on the resources and capacity of the Kenyan government and local institutions to adapt this testing strategy to new populations and cost constraints. Specifically, we will evaluate the following: 1) Implementation elements associated with high uptake of HIV testing, linkage to care and treatment 2) Health facility and individual-level factors that influence fidelity to the aPS intervention 3) Acceptability, demand, and health system requirements influencing feasibility 4) Impact on health outcomes during and after integration of aPS into existing HIV testing services 5) Costs and cost-effectiveness of aPS when integrated into existing HIV testing services Impact: The Kenya Ministry of Health and National AIDS and STI Control Program (NASCOP) have identified assisted partner services as a key strategy for achieving national 90-90-90 goals and recently held a meeting affirming their commitment to scaling up aPS within HIV testing programs. The proposed project will bridge the gap between clinical research findings, everyday practice and public health, and provide much-needed guidance on how to integrate this strategy while retaining its efficacy and ensuring sustainability.